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Name: Nick
Status: educator
Age: 30s
Location: N/A
Country: N/A
Date: 2000

One liter of air containing 4% water vapor by volume(saturated), contains how much liquid water?

You could calculate this from the ideal gas equation of state, pV = nRT, where
p = atmospheric pressure,
V = volume of the sample (= 1 L in this case),
n = the number of moles of gas (unknown in this case),
R = the "universal gas constant," 0.0820575 L atm / (K mol),and
T = the temperature in K; room temperature is about 298 K.

Solving this equation for n tells you how many moles of gas are present. 4% of that is water. Knowing that water weighs 18 g/mole, you can then determine the weight of the water in the 1-L sample of air.

How can this be empirically demonstrated?

Two ways I can think of:

1. Put the sealed sample in a freezer, and weigh the frost that forms on the inside of the container.

2. Place a dessicant in the sealed sample container, and weigh the dessicant after it has absorbed all the water.

I have been unable to find this concept discussed in any chemistry references looked up so far. Perhaps you could direct me to a source where this is talked about.

Here's a really good intro:

You might be able to get something out of these sites as well:

There are many more! Just search on "partial pressure."

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois

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